Web Materials Having Both Plastic and Elastic Properties

ABSTRACT

An extruded web is disclosed. The extruded web can be either a nonwoven material of a films. The web comprises a plasto-elastic material where the plasto-elastic material is a combination of a first polyolefin and a second polyolefin (either a polymeric blends or a polymeric mixture). The claimed combination of polyolefins results in a material that has substantially plastic properties when a sample taken from said web is subjected to an initial strain cycle (such that the web is provided with a set of at least 30% by an initial strain cycle) and substantially elastic properties when a sample taken from the web is subjected to at least a second strain cycle.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 11/087,933,filed Mar. 23, 2005, which claims the benefit of U.S. ProvisionalApplication No. 60/557,225 filed Mar. 29, 2004.

FIELD OF THE INVENTION

The present invention generally relates to web materials suitable foruse in construction of disposable absorbent articles such as diapers,pull-on diapers, training pants, sanitary napkins, wipes, bibs,incontinence briefs or inserts and the like. More specifically, theinvention is directed to web materials that have both plastic andelastic properties. Such materials may be used in the absorbent articlesof the invention to provide the desired article shape and/or to impartthe desired stress and strain properties for improved fit and comfort ofthe article on the wearer and/or for increased convenience of the user.

BACKGROUND OF THE INVENTION

Disposable absorbent products, such as diapers, training pants, andincontinence articles typically include stretchable materials, such aselastic strands, in the waist region and the cuff regions to provide asnug fit and a good seal of the article. Pant-type absorbent articlesfurther include stretchable materials in the side portions for easyapplication and removal of the article and for sustained fit of thearticle. Stretchable materials have also been used in the ear portionsof disposable diapers for adjustable fit of the article. However, itwould be desirable to have materials that exhibit substantially plasticbehavior prior to and during a shaping strain cycle, for example, whenthe article is initially put on a wearer, yet exhibit substantiallyelastic behavior after this initial shaping or donning strain cycle onthe article. In this way, such desirable absorbent articles would havethe ability to shape or size to the wearer to better fit conform to awearer's body shape, yet have the ability to maintain the requiredtension when on a wearer to achieve sustained fit and prevent saggingand/or drooping of the article. Absorbent articles of this kind wouldallow the user or wearer to “permanently” adjust various areas of theabsorbent article, e.g., the crotch or waist region of a diaper, eitherbefore or during the application of the article to the wearer, to adaptthe article to a wearer's body shape. In the case of a diaper, betterfit and comfort can also impart better functional performance such asreduced leakage since the diaper would be better fitting. Such featureshave heretofore not been available for absorbent articles.

There are various approaches to providing desirable stretchableproperties in targeted areas of absorbent articles. Stretchablematerials may be films or nonwoven fibrous webs that include elastomericmaterials. Typically, such materials are stretchable in at least one,and possibly multiple, directions. However, because the films or websare made entirely of elastomeric materials, they are relativelyexpensive, and they tend to have more drag on the skin surface,resulting in discomfort to a wearer of the article. Also, because thematerials are elastomeric, any applied strain is substantially recoveredwhen the force leading to the strain is removed. Sometimes, thestretchable films are laminated to one or more layers of nonwoven webs.Since typical nonwoven webs typically are made of thermoplastic fibers,they have very limited stretchability and, the resulting laminatesprovide considerable resistance to stretch without additionalprocessing. It is necessary to reduce this resistance substantially inorder to make functional stretch laminates. As a result, such materials,have limited ability to shape, size or conform to the particularities ofthe wearer's anatomy upon application.

Other approaches to make stretchable materials are also known,including: stretch-bonded laminates (SBL) and necked-bonded laminates(NBL). Stretch bonded laminates are made by stretching an elastomericmaterial in the machine direction (MD), laminating it to one or morenonwoven substrates while it is in the stretched state, and releasingthe tension in the elastomeric material so that the nonwovens gather andtake on a puckered shape. Necked-bonded laminates are made by firststretching a nonwoven substrate in the machine direction such that itnecks (i.e., reduces its dimension) at least in the cross machinedirection (CD), then bonding the elastomeric material to the substratewhile the substrate is still in the stretched, necked state. Thislaminate will be stretchable in the CD, at least up to the originalwidth of the nonwoven before it was necked. Combinations of stretchbonding and neck bonding have also been known to deliver stretch in bothMD and CD directions. In these approaches, at least one of thecomponents is in a tensioned (i.e., stretched) state when the componentsof the laminates are joined together. Again, these materials cannot beused in absorbent articles to impart sizing or shaping features desiredby users and wearers of absorbent articles.

Zero strain stretch laminates are also known. The zero strain stretchlaminates are made by bonding an elastomer to a nonwoven while both arein an unstrained state. The laminates are then incrementally stretchedto impart stretch properties. The incrementally stretched laminates arestretchable only to the extent afforded by the non-recovered (i.e.,residual) extensibility of the laminate. For example, U.S. Pat. No.5,156,793, issued to Buell et al., discloses a method for incrementallystretching an elastomer-nonwoven laminate web, in a non-uniform manner,to impart elasticity to the resulting laminate. These stretch laminatesbehave similarly to the materials described previously in that they donot have the inherent ability to be adapted to the size or shape of awearer.

The art has also provided “elastic” materials by prestraining asubstantially plastic film so as to provide films having an elastic-likebehavior along at least one axis when subjected to an applied andsubsequently released elongation. Such materials, known as StructuralElastic-Like Films (SELF), are described in U.S. Pat. No. 5,691,035 toChappell.

However, in all the approaches above, the materials or laminates aremade separately and then incorporated into the absorbent article. Forexample, the stretch laminates described herein must be cut into theappropriate size and shape, then adhesively attached to the desiredlocation in the product in a process sometimes referred as the“cut-and-slip” process. Because of the different stretch propertiesrequired for different elements of the product, it is necessary to makea variety of laminates having different stretchability and cut thelaminates to different sizes and shapes. Several cut and slip units maybe needed to handle the different stretchability of the stretchlaminates and to attach them to different locations of the product. Asthe number of cut-and-slip units and/or steps multiplies, the processquickly becomes cumbersome, complicated and expensive. These processesare suitable for modern day absorbent article manufacture and aredesirable. However, it would therefore be desirable to have absorbentarticles having the desired sizing and/or shaping properties, but whichcan be disposed in or on the absorbent article without the need for suchcomplicated and expensive “cut-and-slip” processes.

One alternative to cut and slip processes used by the art is to print anelastomeric composition onto a substrate. Exemplary disclosures includeU.S. Pat. No. 6,531,027 which discusses adhering components of anabsorbent article using an adhesive printing process, PCT ApplicationNo. 03/039420 which discusses printing first and second elastomericcompositions onto a substrate where the compositions differ in at leastone of the following properties: elasticity, melt viscosity,composition, shape, pattern, add-on level, and PCT Application No WO03/053308, which discusses printing an elastic adhesive onto anextendable substrate to provide a tensioning force during garment wear.

The polymer arts have provided materials with stretch properties thatare useful in absorbent article structures. Such materials include:

-   -   Isotactic polypropylene with stereoerrors along the polymer        chain as disclosed in U.S. Pat. No. 6,555,643 and EP 1 256 594        A1;    -   Blends of isotactic polypropylene and alpha-olefin/propylene        copolymers as disclosed in U.S. Pat. Nos. 6,342,565 and        6,500,563 and WO 03/400201; and    -   Block-like isotactic-atactic copolymers as disclosed in U.S.        Pat. Nos. 6,559,262, 6,518,378 and 6,169,151.

Based on the foregoing, it would be desirable to have absorbent articleswith stretchable material having both elastic and plastic propertiessuch that it can be sized or shaped as desired but still retains thedesired degree of elasticity to facilitate sustained fit on the wearer.Although not always necessary, it would be desirable to have such amaterial that can be disposed easily on any specific area of theabsorbent article in any desired amount. Additionally, it would bedesirable to have such a material or composite having plastic andelastic properties that can be easily placed in discrete, spaced apartareas of the absorbent article via known techniques such as a“cut-and-slip” process.

SUMMARY OF THE INVENTION

In one aspect of the invention, the plasto-elastic material hassubstantially plastic properties when it is subjected to an initialstrain and having substantially elastic properties when it is subjectedto a second strain cycle. In other aspects of the invention, thematerial used in the absorbent article has, according to a HysteresisTest, at least about a 15% set upon a first application of a strain of200%, and less than about a 15% set upon a second application of astrain of 50%. Typically, such materials also have a force at 25%elongation of between 0.005 N/cm and about 50 N/cm after the firstapplication of a 200% strain.

In another aspect of the invention the plasto-elastic material isadvantageously extruded into a fiber for use in a nonwoven material.Such fibers may comprise only the plasto-elastic material or they may bebicomponent fibers comprising at least one additional material. Theadditional material may be either a polymeric compound havingsubstantially plastic stress-strain properties or the additionalmaterial may be a polymeric compound having substantially elasticproperties.

In yet another aspect of the invention the plasto elastic material maybe formed into a film structure using known extrusion techniques such asfilm casting and film blowing. Such films may comprise only theplasto-elastic material or they may be coextruded films comprising atleast one additional material. The additional material may be either apolymeric compound having substantially plastic stress-strain propertiesor the additional material may be a polymeric compound havingsubstantially elastic properties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of data from an hysteresis evaluation of a nonwovenmaterial comprising the plasto-elastic materials of the presentinvention.

FIG. 2 is a graph of data from an hysteresis evaluation of an extrudedfilm comprising the plasto-elastic materials of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Definitions

As used herein, the term “polymeric blend” means a mixture of polymerswhich includes, but is not limited to, homopolymers, copolymers (e.g.,block, graft, random and alternating copolymers), terpolymers, etc., andblends and modifications thereof which is in the form of a solidsolution, that is a homogeneous mixture. Optional adjuncts may be addedto the polymeric blend and, if the blend remains a solid solution, suchblends are also considered polymeric blends.

As used herein, the term “polymeric mixture” means a mixture of at leasttwo polymeric materials, in which at least a portion of one or more ofthe polymeric materials is immiscible in at least a portion of anotherof the polymeric materials, i.e., the mixture is heterogeneous.

By “stretch”, it is meant that the material has the ability to extendbeyond its original length in at least one dimension when subjected to atensile force (i.e., tension) applied in the direction of thatdimension. “Stretch” may be unidirectional, bi-directional, ormulti-directional. The specific “stretch” properties of a material mayvary along any of the stretch vectors. As used herein, stretch includesboth elastic and plastic deformation.

By “elastic” or “elasticity”, it is meant that a material has theability to return to substantially its original pre-stretched dimensionafter an elongation-relaxation cycle such as subjecting it to tension ora force in that dimension and then releasing the elongating tension onthe material (i.e., allowing the material to relax).

By “plastic”, “plasticity”, “extensible”, or “extensibility”, it ismeant that a material has the ability to elongate in at least onedirection under an applied tensile force without significant return whenthe force is removed. Substantially non-recoverable deformation isreferred to as plastic deformation.

By “plasto-elastic” and “plasto-elasticity”, it is meant that a materialhas the ability to stretch in a substantially plastic manner during aninitial strain cycle (i.e., applying a tensile force to induce strain inthe material, then removing the force allowing the material to relax),yet exhibit substantially elastic behavior and recovery duringsubsequent strain cycles. It will also be recognized that anelasto-plastic material and elasto-plasticity are equivalent descriptorsof such materials.

As used herein, the term “joined” encompasses configurations whereby anelement is directly secured to another element by affixing the elementdirectly to the other element, and configurations whereby an element isindirectly secured to another element by affixing the element tointermediate member(s) which in turn are affixed to the other element.

As used herein, the term “disposed” is used to mean that an element(s)is formed (joined and positioned) in a particular place or position as aunitary structure with other elements or as a separate element joined toanother element.

As used herein, the term “joined” encompasses configurations whereby anelement is directly secured to another element by affixing the elementdirectly to the other element, and configurations whereby an element isindirectly secured to another element by affixing the element tointermediate member(s) which in turn are affixed to the other element.

A “unitary” absorbent article refers to absorbent articles which areformed of separate parts united together to form a coordinated entity sothat they do not require separate manipulative parts like a separateholder and liner.

As used herein, the term “diaper” refers to an absorbent articlegenerally worn by infants and incontinent persons about the lower torso.

“Longitudinal” is a direction running parallel to the maximum lineardimension of the article and includes directions within ±45° of thelongitudinal direction. The “lateral” or “transverse” direction isorthogonal to the longitudinal direction. The “Z-direction” isorthogonal to both the longitudinal and transverse directions. The “x-yplane refers to the plane congruent with the longitudinal and transversedirections.

The term “substrate” as used herein refers to any material, including afilm, an apertured film, a nonwoven web, a woven web, a foam or acombination thereof, or a dry lap material including wood pulp,cellulosic, derivatized or modified cellulosic materials, and the like,having a single layer or multiple layers. The term “fibrous substrate”as used herein refers to a material comprised of a multiplicity offibers that could be either a natural or synthetic material or anycombination thereof, including, for example, nonwoven materials, wovenmaterials, knitted materials, and any combinations thereof.

The term “nonwoven” as used herein refers to a fabric made fromcontinuous filaments and/or discontinuous fibers. Nonwoven fabricsinclude those made by carding staple fibers, airlaying or wet layingstaple fibers and via extrusion processes such as spunbonding and meltblowing. The nonwoven fabric can comprise one or more nonwoven layers,wherein each layer can include continuous filaments or discontinuousfibers. Nonwovens can also comprise bi-component fibers, which can haveshell/core, side-by-side, or other known fiber structures.

By “shaping strain cycle” is meant the steps of applying a tensile forceto extend a plasto-elastic material to a desired elongation, thensubsequently removing the tensile force and allowing the sample torelax, generating a substantial amount of permanent “set” or deformationin the material.

Preferred Embodiments

In a preferred embodiment, the invention provides a web of materialwhich may be stretched into a new geometry, such as a larger size and/ordifferent shape, substantially permanently, and thereafter, is elasticin that the larger sized or reshaped article may expand andsubstantially contract back to this new geometry. Such webs areparticularly useful as materials for use in absorbent articles, such asdiapers, pull-on diapers, training pants, sanitary napkins, wipes, bibs,incontinence briefs or inserts in that the article can be packaged,shipped and stored in a compact size for convenience prior to use, andthen when used, removed from the package and expanded to be donnedconveniently on the wearer. Once on the wearer, the article may beelastically expanded and contracted for good fit and comfort. In thecontext of this invention, the expansion or extendibility of the articlewhen subjected to the initial stretch or pull can be referred to as the“plastic” deformation of the article in that the article substantiallyretains its new geometry. It should be understood that this new geometrydoes not need to be retained perfectly since those skilled in the artwill appreciate that a certain amount of contraction and extensibilitygenerally exists in most plastic materials. In other words, thepermanency of the initial plastic deformation of the article sometimesmay not perfect. In a similar fashion, the elasticity of the articleupon subsequent stretch, pull or tension after the initial force also isnot perfect, but like the initial plastic deformation, generally may beelastic at the plastically deformed new geometry of the article.

Stated differently, the present invention provides materials useful inabsorbent articles that exhibit substantially plastic behavior prior toand during a shaping strain cycle, yet exhibit substantially elasticbehavior after the initial shaping strain cycle during subsequent straincycles. For example, an absorbent article may employ such aplasto-elastic material in its plastically deformable state (i.e., priorto a shaping strain cycle) such that the wearer or caregiver mayselectively elongate at least a portion of the plasto-elastic materialin a straining cycle to adapt the shape of the article for convenientdonning and better fit for the wearer and to establish zones ofpost-straining cycle elasticity. Alternatively, at least a portion ofthe article's plasto-elastic material may be subjected to a shapingstrain cycle to create a desired article shape and establish zones ofelasticity after the shaping strain during manufacture of the article.

Plasto-Elastic Materials

A plasto-elastic material suitable for use in the absorbent article has,according to a Hysteresis Test described in more detail hereinafter, atleast about a 15% set upon a first application of a strain of 200%, andless than about a 15% set upon a second application of a strain of 50%.Typically, plasto-elastic materials have at least about 30% set uponrelaxation from an initial 200% strain. More preferably, plasto-elasticmaterials exhibit more than about 40% set, more preferably more thanabout 50%, and most preferably, more than about 70%. Such materialstypically have a set between about 30% and about 140% after a firststrain cycle of 200%, more typically between about 30% and about 120%and still more typically between about 40% and about 100%.

In subsequent strain cycles, the plasto-elastic materials of the presentinvention that have been prestrained to 200% exhibit less than about 15%set, preferably less than about 12% set and more preferably less thanabout 10% set after relaxation from a second strain of 50%.

Plasto-elastic materials also may exhibit low force relaxation when heldin an at least partially extended state for an extended period of timein a strained configuration after a first strain cycle. Typicalplasto-elastic materials that have been prestrained to 200% exhibit lessthan about 70% force relaxation, preferably less than about 60%, morepreferably less than 50%, and most preferably less than about 40% whileheld at 50% strain for 4 hours at 38° C. The force relaxation behavioris similar when held in a strained configuration at lower temperatures.Specifically, prestrained (200%) plasto-elastic materials exhibit lessthan about 70% force relaxation, preferably less than about 60%, morepreferably less than 50%, and most preferably less than about 40% whileheld at 50% strain for 30 seconds at 25° C.

Such desirable force relaxation behavior is particularly evident whenthe elastic component of the plasto-elastic material comprises more thanone elastic material. As can be seen in Example 2, such blends can havethe beneficial aspects of each of the constituent elastic materials.

Suitable materials have a force at 25% elongation of between 0.005 N/cmand about 50 N/cm after the first application of a 200% strain.Preferably the materials have a force at 25% strain of between about0.05 N/cm and about 15 N/cm more preferably between about 0.01 N/cm andabout 5 N/cm. In certain embodiments the elastic resistance ranges fromabout 0.1N to about 3 N/cm.

In order to help insure absorbent article features that are prestrainedduring the manufacturing process maintain their prestrainedconfiguration throughout the distribution system, the plasto-elasticmaterials of the present invention preferably maintain their prestraineddimensions when exposed to elevated temperatures for extended times.Suitably, dimensions after a first strain cycle are reduced less thanabout 20% after unconstrained exposure to 60° C. for two minutes.Preferably, such dimensional reduction is less than about 15%, morepreferably less than about 10%. Suitable plasto-elastic stretchmaterials, comprise multi-component polyolefin compositions thatcomprise a combination of at least one elastic component and at leastone component which causes the composition to exhibit plastic behaviorduring a first strain cycle. Such compositions are described more fullyin the following sections.

Elastic Component

The elastic component functions to provide the desired amount and forceof recovery upon the relaxation of an elongating tension on theplasto-elastic material, especially upon strain cycles following theinitial shaping strain cycle. Many elastic materials are known in theart, including synthetic or natural rubbers (e.g., crosslinkedpolyisoprene, polybutadiene and their saturated versions (afterhydrogenation) and polyisobutylene), thermoplastic elastomers based oneither multi-block copolymers such as those comprising copolymerizedrubber elastomeric blocks with polystyrene blocks (e.g.,styrene/isoprene/styrene or styrene/butadiene/styrene) or polyurethanes,which form a hard glassy phase which when dispersed in the elastomericphase, anchor the polymer chains together so as to provide highmechanical integrity. Preferred elastic components include ethylene andpropylene-based elastomers.

Ethylene-rich elastomers may be polymerized with various amounts ofcomonomers more or less randomly incorporated in the backbone in orderto significantly reduce the crystallinity of the ethylene-rich backbone.Unsaturation may also be incorporated along the chain to providereactive sites for subsequent cross-linking or vulcanization reactionsvia sulfur chemistry or via exposure to radiation. Crosslinkingreactions link polymeric chains to one another, resulting in greatershape recoverability by minimizing chain slippage that may lead toundesirable creep or stress relaxation. Ethylene-rich elastomersfunctionalized with small amounts of other chemical moieties may alsoprovide sites for subsequent strong polar interactions (as in ionomers)or for subsequent crosslinking reactions (moisture-crosslinkablesilane-modified polyethylene). Ethylene-rich elastomers having atailored composition, molecular weight and narrow composition andmolecular weight distributions may also be produced usingmetallocene-based catalysis. In other words, the amount of residualethylene-based crystallinity may be controlled and can function asphysical crosslinks and chain-anchoring entities capable of providingincreased mechanical stability and integrity to the material.

Particularly preferred elastic components include propylene-richelastomers. In these materials, propylene represents the majoritycomponent of the polymeric backbone, and as a result, any residualcrystallinity possesses the characteristics of polypropylene crystals.As in the case of ethylene-based elastomers, residual crystallineentities embedded in the propylene-based elastomeric molecular networkmay function as physical crosslinks, providing polymeric chain anchoringcapabilities that improve the mechanical properties of the elasticnetwork, such as high recovery, low set and low force relaxation.

An alternative means of providing anchoring capabilities is to blendinorganic particles into an amorphous polymer matrix. Suitable particlesmay be either microscopic (equivalent diameter >0.1 microns) ornanoscopic (equivalent diameter <0.1 microns) in size. For example, theuse of microscopic inorganic filler materials in polyolefin plasticcomponents of the present invention may promote the formation ofmicropores during tensile loading and increase the moisture vaportransmission of the material which is beneficial to the internal climateof the disposable absorbent product.

Preferred elastomeric materials comprise polypropylene polymers andinclude:

-   a) Polypropylene polymers comprising crystalline isotactic blocks    and amorphous atactic blocks. In this case the crystalline blocks    serve as the “anchoring” points for the amorphous blocks that lie    between such anchors. Such materials are disclosed, for example in    U.S. Pat. Nos. 6,559,262, 6,518,378 and 6,169,151.-   b) Isotactic polypropylene with stereoerrors along the polymer chain    as disclosed in U.S. Pat. No. 6,555,643 and EP 1 256 594 A1.-   c) Polypropylene polymers that incorporate a low level of a co    monomer, such as ethylene or a higher α-olefin into the backbone to    form an elastomeric random copolymer (RCP). Exemplary materials    include: VISTAMAXX as is available from ExxonMobil Chemical Co. of    Houston, Tex. and OLYMPUS as is available from the Dow Chemical    Company of Midland, Mich.

In another embodiment of the present invention, the elastic componentmay comprise a blend of elastic materials. As noted above and in Example2 such blends contribute particularly desirable force relaxationproperties. In a particularly preferred embodiment of this type theelastic component comprise a combination of a polypropylene elastomerand a styrenic block copolymer.

Plastic Component

The plastic component of the plasto-elastic compositions of the presentinvention functions to provide the desired amount of permanent plasticdeformation imparted to the material during the initial shaping straincycle. The higher the concentration of a given plastic component in theplasto-elastic composition, the greater the possible permanent “set”following relaxation of an initial straining force on the material.Preferred plastic components include higher crystallinity polyolefinsthat are themselves intrinsically plastically deformable when subjectedto a tensile force in one or more directions. Exemplary polyolefins ofthis type include certain linear low density polyethylenes (linear lowdensity polyethylenes), high density polyethylenes (HDPEs),polypropylene homopolymers with and random copolymers of propylene and asmall fraction of another monomer such as ethylene (plastic RCPs) havinga melt temperature greater than about 80° C., multi-phase systems wherea rubber is dispersed in a plastic phase also known as impact copolymers(ICPs), syndiotactic polypropylene, polybutene, polyolefin waxes andtheir blends. Suitable polyolefin plastic components may be eithermiscible or immiscible with the elastic component. Preferred polyolefinplastic component materials are at least partially immiscible with thematerial that constitutes the elastic component so as to facilitate theinterpenetrating network discussed below. For example, in embodimentswherein the elastic component of the plasto-elastic material is of thestereoisomer type described above, a RCP matrix of intermediatecrystallinity (low to medium ethylene content) is a preferred plasticcomponent (e.g., WINTEC WFX4T available from Japan Polypropylene (Tokyo,Japan)). Alternatively, if the elastic component is of the randomcopolymer type, then a medium or high melt temperature polypropylenehomopolymer or linear low density polyethylene is a preferred plasticcomponent (e.g., ACHIEVE from ExxonMobil Chemical Company of Houston,Tex.).

Alternate polymorphic forms of the polyolefin plastic component may alsobe suitable. For example, beta-crystalline forms of polypropylene mayprovide an easily deformable, highly ductile, tough plastic component.Upon tensile deformation, beta-crystalline polypropylene may alsodevelop microvoids, increasing the transport properties (e.g., theability to transport water vapor therethrough) of the plastic component,and ultimately the plasto-elastic material.

A particularly preferred plastic component is a polyolefin wax. Suitablematerials of this type include microcrystalline waxes, low molecularweight polyethylene waxes and poly propylene waxes. Such waxes areadvantageously used between about 5% and about 50% of the plasto-elasticcomposition, preferably between about 10% and about 40%. Exemplarymaterials include but are not limited to: a microcrystalline waxavailable from the Crompton Corporation of Middlebury, Conn. as MultiwaxW-835; a low melting refined petroleum wax available from the ChevronTexaco Global Lubricants of San Ramon, Calif. as Refined Wax 128; a lowmolecular weight polyethylene as is available from Honeywell Specialtywax and Additives of Morristown, N.J. as A-C 735 and a low molecularweight polypropylene as is available from Clariant, Pigments & AdditivesDivision of Coventry, R.I. as Licowax PP230.

Plasto-Elastic Compositions

The structural and morphological characteristics of the elastic andplastic components within the plasto-elastic material, driven largely bythe plasto-elastic blending process, are critical to the resultantstress-strain properties of the plasto-elastic material. Specifically,it is important to achieve micro-scale dispersion of any immisciblecomponents (i.e., any discernable domains have an equivalent diameterless than about 10 microns). A suitable blending means is a twin screwextruder (e.g., the Polylab Twin Screw Extruder (available from ThermoElectron (Karlsruhe), Karlsruhe, Germany)) as are known to the art.Multicomponent polymer blend morphologies are typically dependent uponmany factors such as the relative fraction and the melt rheology of eachof component, their relative viscosity, as well as the compatibility ofthe various plastic and elastic components. For example, finer blendmorphologies may be achieved between polymers having a greaterthermodynamic affinity.

Suitable plasto-elastic compositions may comprise from about 95% toabout 5%, by weight, of the elastic component, and preferably from about90% to about 40%, by weight, of the elastic component. Preferably, theplasto-elastic, compositions may comprise from about 5% to about 95%,and more preferably from about 10% to about 60%, by weight, of theplastic component. In some embodiments, the plasto-elastic compositionmay comprise more than two major components (i.e. more than twocomponents are used at a level that is greater than about 5%).

The combination may be either in the form of a polymeric blend or apolymeric mixture, depending upon the degree of miscibility of theelastic and plastic components. If the combination forms a blend, onecomponent can form the continuous phase that encloses dispersedparticles of the other component(s). Preferably, the plasto-elasticcomposition comprises an interpenetrating blend having a co-continuousmorphology with both phases forming interpenetrating networks.

Importantly, the polyolefin-based materials comprising theplasto-elastic composition are chosen so as to exhibit a uniquecombination of the plastic characteristic of traditionalhigh-crystallinity polyolefins and the elastic characteristic oftraditional elastomers. More specifically, the materials are chosen soas to provide the following mechanical performance profile to theplasto-elastic composition:

-   a) A low-force plastic (i.e., “permanent”) deformation in response    to an initial deformation strain cycle at a temperature of about    room temperature and extending up to and including a temperature at,    or slightly greater than, normal body temperature. Suitably, the    “permanent” deformation extends is at least about 30% of the overall    applied strain, preferably at least about 50%, more preferably at    least about 70%. The applied strain can be either uniaxial or    multivector.-   b) The pre-stretched material then exhibits substantially elastic    behavior upon multiple subsequent deformation cycles with low set,    high recovery and low force relaxation at temperatures up to and    including body temperature, especially over the range of strain    applied during the original deformation cycle.    A suitable plasto-elastic material will have:-   a) A relative amount of permanent dissipative viscoplastic    deformation ranging from 15% to 140% of the initial strain cycle,    for maximum extension values ranging from 50 to 500%, at    temperatures ranging from about 20° C. to about 100° C. and initial    strain rates ranging from 0.01 to 2000 s⁻¹. Preferably, the material    can be deformed without failure at strain rates between about 1 to    2000 s⁻¹, more preferably 50 and 2000 s⁻¹, still more preferably at    strain rates between 1000 and 2000 s⁻¹.-   b) A dimensional stability of the material following the first    loading cycle upon exposure to a temperature of up to 60° C.    characterized by less than 20% change in the macroscopic dimensions    of the material as measured by the Dimensional Stability in Storage    Conditions test described in the TEST METHODS section below.-   c) A permanent set value of less than 15% upon an extension of the    material by a subsequent loading to a strain of at least 30%    (preferably 40% and even more preferably 50%). Preferably the set is    less than 10% of the strain applied upon each subsequent strain    cycle;-   d) A percent force relaxation less than 70%, preferably less than    50% at 50% strain (i.e., 150% elongation), for periods of up to 10    hr and for temperatures up to 40° C.

Fibers/Nonwovens

It has also been found that fibers comprising the plasto-elasticcompositions described herein and nonwoven materials provideadvantageous features when used as a component of a disposable absorbentarticle. Such features include, but are not limited to selectiveadjustability to fit a variety of body shapes because the fiber/nonwovenmaterial facilitates “permanent” adjustment of portions of an absorbentarticle via plastic deformation and, at the same time, the article cancontinue to conform to a wearer's body throughout a wide range of bodymotion via elastic extensibility and efficient material utilizationbecause a nonwoven comprising fibers of a plasto-elastic material can beselectively stretched to form a predefined shape during themanufacturing process thus reducing the amount of material that isdiscarded as scrap.

The fibers may be of any suitable size, that is the fiber may have adiameter or equivalent diameter of from about 0.5 micron to about 200microns. Fiber diameters or equivalent diameters between about 10 andabout 40 microns are particularly preferred. Said another way, fibersincorporating the plasto-elastics of the present invention are suitablybetween about 1 and about 10 denier, preferably between about 1 andabout 8 denier, more preferably between about 1 and about 5 denier.

In one embodiment, the fibers comprise bicomponent fibers for improvedconsolidation. Bicomponent fibers are typically used as a means ofbetter dissociating intrinsic fiber characteristics and bondingperformance, the latter being typically dominated by the sheath in thecase of bicomponent fibers. As is well known, a bicomponent fibercomprises first and second polymeric components that are coextruded soas to provide the fiber with certain desirable properties from each ofthe polymeric components (As will be recognized both the first andsecond polymeric components comprise thermoplastic polymers). Forexample a bicomponent fiber can comprise a first polymeric componenthaving a lower softening temperature than the second polymericcomponent. Such structures reduce the risk of “burn through” duringthermal consolidation.

The bicomponent fiber may be of any suitable configuration. Exemplaryconfigurations include but are not limited to sheath-core, island-in-thesea, side-by-side, segmented pie and combinations thereof. In oneoptional embodiment of the present invention the bicomponent fibers havea sheath-core configuration.

Spunbond structures, staple fibers, hollow fibers and shaped fibers suchas multi-lobal fibers can all be produced which comprise theplasto-elastics and mixtures of the present invention. The fibers of thepresent invention may have different geometries that include round,elliptical, star shaped, rectangular, and other various eccentricities.

The bicomponent fibers have a size comparable to those comprising onlythe plasto-elastic or mixture of the present invention. That is thefiber may have a diameter or equivalent diameter of from about 0.5micron to about 200 microns. Fiber diameters or equivalent diametersbetween about 10 and about 40 microns are particularly preferred. Saidanother way, fibers incorporating the plasto-elastics of the presentinvention are suitably between about 1 and about 10 denier, preferablybetween about 1 and about 5 denier, more preferably between about 1 andabout 3 denier.

As noted above, the bicomponent fibers comprise a first polymericcomponent and a second polymeric component. In specific embodiments ofthe present invention the first polymeric component comprises theplasto-elastic materials discussed above and the second polymericcomponent may comprise either a polymeric material having substantiallyelastic properties or a polymeric material having substantially plasticproperties. As will be recognized, such specific embodiments can betailored to have wide variety of mechanical properties depending on theparticular combination of materials that is chosen.

The amount of first polymeric component and second polymeric componentpresent in the bicomponent fiber will depend upon many factors, such asbut not limited to, polymers present, desired use of bicomponent fiber,desired properties of the bicomponent fiber, etc. In one optionalembodiment the weight ratio of the first polymeric component to thesecond polymeric component is from about 1:20 to about 20:1.

Typically, the fibers described above are consolidated into a nonwovenmaterial. Consolidation can be achieved by methods that apply heatand/or pressure to the fibrous web, such as thermal spot (i.e., point)bonding. Thermal point bonding can be accomplished by passing thefibrous web through a pressure nip formed by two rolls, one of which isheated and contains a plurality of raised points on its surface, as isdescribed in U.S. Pat. No. 3,855,046. Consolidation methods can alsoinclude, but are not limited to, ultrasonic bonding, through-airbonding, resin bonding, and hydroentanglement. Hydroentanglementtypically involves treatment of the fibrous web with high pressure waterjets to consolidate the web via mechanical fiber entanglement (friction)in the region desired to be consolidated, with the sites being formed inthe area of fiber entanglement. The fibers can be hydroentangled astaught in U.S. Pat. Nos. 4,021,284 and 4,024,612.

Once consolidated, the web can be further processed (i.e., converted).For example, the web, either alone or in the form of a laminate withanother material can be further processed to impart stretchabilitythereto. Methods for imparting stretchability to an extensible orotherwise substantially inelastic material by using corrugatedinterengaging rolls which incrementally stretch in the machine orcross-machine direction and permanently deform the material aredisclosed in U.S. Pat. No. 4,116,892, U.S. Pat. No. 4,834,741, U.S. Pat.No. 5,143,679, U.S. Pat. No. 5,156,793, U.S. Pat. No. 5,167,897, U.S.Pat. No. 5,422,172, and U.S. Pat. No. 5,518,801. In some embodiments,the intermediate structure may be fed into the corrugated interengagingrolls at an angle with respect to the machine direction of thissecondary operation. Alternatively, the secondary operation may employ apair of interengaging grooved plates applied to the intermediatestructure under pressure to achieve incremental stretching of theintermediate structure in localized portions. As noted above, thenonwoven webs of the present invention are particular suitable for theseand similar processes because of their particularly desirable coldextensibility.

Nonwoven materials comprising the plasto-elastic materials of thepresent invention are particularly useful as a component of a disposableabsorbent article (e.g., as a topsheet, a cuff material, a core wrap,and when laminated to a film or, otherwise, treated to be substantiallyimpermeable to aqueous liquids as a backsheet). Although the nonwovenweb of the present invention can find beneficial use as a component of adisposable absorbent article, such as but not limited to, disposablediapers, disposable incontinence briefs, disposable training pants,disposable pads or sheets for floor cleaning systems, such as theSWIFFER® cleaning system manufactured by The Procter & Gamble Company,catamenial products, disposable wipes, and the like; its use is notlimited to disposable absorbent articles. The nonwoven web of thepresent invention can be used in any application requiring, orbenefiting from a combination of elasticity and durable extensibility.

Films

In other embodiments, the plasto-elastic materials of the presentinvention may be advantageously employed in the extrusion of films. Suchfilms may be produced using known processes such as casting. Theplasto-elastic material may also be extrusion coated onto a nonwovensubstrate effectively forming a film layer thereon.

Films comprising the plasto-elastic materials of the present inventionmay be monolithic (i.e. comprising only the plasto-elastic material).Alternatively, the plasto-elastic material may comprise a layer of acoextruded film. As will be recognized, such coextruded films mayfurther include layers comprising other materials such as materialshaving substantially elastic properties or materials havingsubstantially plastic properties.

Films according to the present invention find utility as components ofabsorbent articles. For example, such a film could provide liquidimpermeability to a backsheet while also providing the capability toshape the backsheet. Alternatively such film may also be used to provideelastomeric contractions to, for example, a side panel of a disposableabsorbent article. In this embodiment the plasto-elastic film providesinitial adjustability to a particular body configuration via shapingstrain cycle an then conformity to the body during wear due to itselastic property.

For end uses such as absorbent articles, such films should be thin andflexible. Desirably, a film comprising the plasto-elastic materials ofthe present invention has a caliper less than about 200 microns,preferably less than about 100 microns, more preferably less than about50 microns. In order to have suitable durability, particularly duringthe manufacturing process, a film according to the present inventionshould have a caliper greater than about 10 microns.

Film basis weight is suitably greater than about 10 g/m², preferablygreater than about 15 g/m². Desirably, films for use as a backsheetmaterial have a basis weight between about 15 g/m² and about 35 g/m². Aswill be recognized, films used in other absorbent article componentshave different desirable ranges of basis weight. For example, films foruse in a side panel desirably have a basis weight between about 40 g/m²and about 80 g/m².

Substrate

In certain embodiments of the present invention, the web materialsdescribed herein may be laminated to a substrate. Laminates may becombined by any number of bonding methods known to those skilled in theart including, but not limited to, thermal bonding, adhesive bondingincluding, but not limited to spray adhesives, hot melt adhesives, latexbased adhesives and the like, sonic and ultrasonic bonding, andextrusion laminating whereby a polymer is cast directly onto anothernonwoven, and while still in a partially molten state, bonds to one sideof the nonwoven, or by depositing melt blown fiber nonwoven directlyonto a nonwoven. These and other suitable methods for making laminatesare described in U.S. Pat. No. 6,013,151 and U.S. Pat. No. 5,932,497.

Suitable substrate materials include but are not limited to: films,apertured films, foams, knitted fabric, woven fibrous webs or nonwovenfibrous webs as are known in the art. In some embodiments, thesubstrates are extensible nonwoven webs made of polyolefin fibers orfilaments, such as polyethylene, or polypropylene. The substratematerial may be elastic or inelastic, extensible or inextensible,stretchable or non-stretchable. Preferred substrates have a3-dimensional morphology (i.e., via spacing between fibers, projections,holes, etc.) that facilitates the penetration of the thermoplasticelastomer into the substrate as described below.

Such substrate materials may suitably be formed from polymeric resinshaving either substantially elastic properties or substantially plasticproperties so as to provide the substrate material with similarproperties. As will be recognized, a laminate comprising aplasto-elastic web according to the present invention with a substratehaving predefined stress/strain properties as may be chosen by adesigner of absorbent articles gives the designer a wide range ofoptions to meet particular design requirements.

In some embodiments the substrate cooperates with the plasto-elasticmaterial to provide a limit to how much the plasto-elastic material maybe strained during an initial strain cycle. Such limits can beadvantageous, for example, when the plasto-elastic material is intendedto provide a degree of size adjustability to a feature of an absorbentarticle where it would be undesirable for the extent strain cycle to beover large (e.g., preventing stretching a waistband so it is larger thanthe circumference of a wearer's waist). Such a limitation could beprovided, for example, by disposing the plasto-elastic material onto thesubstrate while the substrate is in a shined condition or by providing asubstrate that is elastic in and of itself so that it provides a tactilesignal of increasing strain to a caregiver. Suitably, a substrate ofthis type limits the initial strain cycle initial strain cycle such thatthe initial strain cycle elongates the plasto-elastic material no morethan 100%. Optionally, the substrate limits the initial strain cyclesuch that the initial strain cycle elongates the plasto-elastic materialno more than 75%.

Converting Processes

The web materials of the present invention are suitable for most typicalconverting processes used in the production of an absorbent article.Such processes include, but are not limited to neck bonding and stretchbonding as described above. The web materials may also be used toproduce SELF materials as described in U.S. Pat. No. 5,691,035 and toproduce zero strain stretch laminates as described in U.S. Pat. No.5,156,793. When the web materials of the present invention are stretchedin a converting process they may be stretched either uniaxially or alongmore than one axis (e.g. biaxially). The process of shaping the materialinto a form different than the original one can take place in severalindependent steps. The plasto-elastic web also may be printed, extrusioncoated or adhesively attached to other webs using known processes toform laminated structures with plasto-elastic properties. It isimmaterial whether such other webs are elastic or plastic, films ornonwovens.

EXAMPLES Comparative Example 1

This example describes film formation from two resins of the prior art:an experimental grade of ADFLEX 7573 (a reactor blend of anethylene-based elastomer and polypropylene available from BasellPolyolefins of Wilmington, Del.) (1-1); an isotactic polypropylene withstereoerrors along the polymer chain as disclosed in U.S. Pat. No.6,555,643 (1-2); a high-performance blend typically used in diaperstretch components comprising a styrenic block copolymer available fromKuraray Co. Ltd. of Tokyo, Japan as Septon 4033 (1-3); an elastomericpolypropylene as is available from Exxon Mobil Chemical of Huston, Tex.as VISTAMAXX 1100 (1-4); and two blends of a very low densitypolyethylene (EXACT 4049 from Exxon Mobil of Huston, Tex.) and a linearlow density polyethylene (LL6201 from Exxon Mobile Chemical of Huston,Tex.) where ID 1-5 is 85% VLDPE/15% LLDPE and 1-6 is 70% VLDPE/30%LLDPE. Tables 1 and 2 list film properties.

TABLE 1 Initial Final Film load @ load @ Force Compo- Prestrain Specimenbasis 50% 50% Relax. sition Temperature width weight strain¹ strain¹ (10hrs) ID (° C.) (mm) (g/m²) (N) (N) (%) 1-1 23 12.7 97 3.44 1.49 57 1-223 12.7 141 1.06 0.54 49 1-3 23 15.9 179 0.61 0.44 28 1-4 23 19.0 1510.99 0.40 59 1-5 23 12.7 143 2.27 0.98 57 1-6 23 12.7 103 2.24 1.14 49¹Normalized to 150 g/m² and 6.4 mm width

TABLE 2 a 1st Cycle 2nd Cycle (200%, RT) (50%, R.T.) Stress % @ Force200% % Set Stress Relax- Stress @ % Set Basis Pre- after 1st @ ation 30%after 2nd Blend Weight strain Cycle 50% @ 50% Unload Cycle ID g/m² MPa %MPa % MPa % 1-1 111 6.88 87.9 6.36 51.4 0.25 15.3 1-2 154 2.74 3.9 1.2418.8 0.64 6.7 1-3 128 1.13 5.4 0.64 7.5 0.39 4.0 1-4 148 1.75 13.6 0.9517.4 0.45 6.7 b 1st Cycle 2nd Cycle (300%, RT) (200%, R.T.) Stress % @Force 200% % Set Stress Relax- Stress @ % Set Blend Basis Pre- after 1st@ ation 30% after 2nd ID Weight strain Cycle 50% @ 50% Unload Cycle 1-5180 3.54 74.2 4.15 29.8 * >30% 1-6 168 4.14 86.5 5.12 32.0 * >30% *Stress too low to measure

As can be seen: 1) the polyethylene-containing blends typically have arelatively high stress at both 200% and 50% elongations (related tostiffness), 2) a high force relaxation after a second elongation cycle(>15%) and, sometimes, 3) negligible stress at 30% elongation during theunload of the second cycle and/or a high level of additional set after asecond loading cycle.

Example 2

This example illustrates the properties of blends of two differentelastomeric polyolefins.

The blends shown in Table 3 were compounded in a batch mixer availablefrom Haake Polylab of Newington, N.H. Fifty gram batches were processedfor about 6 min at 170° C. Commercially available antioxidants were alsoadded to the mix at a low level (<1%) to help protect the blend fromthermal/oxidative degradation.

TABLE 3 Elastomeric Elasto- Very Low Reactor Composi- Isotactic mericDensity Polypro- tion Polypro- Polypro- Polyeth- Styrenic pylene IDpylene¹ pylene² ylene³ Blend⁴ Copolymer⁵ 2-1 40 60 2-2 60 40 2-3 20 802-4 40 60 2-5 20 80 2-6 40 60 2-7 85 15 ¹Isotactic polypropylene withstereoerrors along the polymer chain as disclosed in U.S. Pat. No.6,555,643 ²VISTAMAXX 1100 as is available from Exxon Mobil Chemical ofHuston, TX. ³EXACT 4049 as is available from Exxon Mobil Chemical ofHuston, TX. ⁴High-performance blend typically used in diaper stretchcomponents comprising a styrenic block copolymer available from KurarayCo. Ltd. of Tokyo, Japan as Septon 4033 ⁵Soft polypropylene-basedthermoplastic elastomer reactor blend produced using Catalloy technologyand available as ADFLEX 7353 from Basell Polyolefins of Elkton, MD.Properties of the films are shown in Tables 4 and 5.

Compression-molded films were prepared with a Carver press (Availablefrom Carver, Inc. of Wabash, Ind.) using the following steps:

-   1. Place a Teflon® template (A Teflon® sheet with the center area    cut away to define the sample area). The thickness of the sheet    determines the thickness of the sample.) on a 0.005″ thick Teflon®    sheet. Place composition to be formed onto the press, in the open    area of the template. Cover with a second 0.005″ thick Teflon®    sheet.-   2. Place the Teflon® sheets/composition “sandwich” between heated    (200° C.) platens of the Carver Press and slowly load to 5,000    pounds of pressure. Wait 30 seconds.-   3. Increase pressure to 12,000 lbs and wait 60 seconds.-   4. Release pressure, rotate the Teflon® sheets/composition    “sandwich”180° and load to 12,000 lbs. Wait 30 seconds and release    pressure.-   5. Immediately remove the Teflon® sheets/composition “sandwich” and    cool it between room-temperature metal plates.-   6. If the film that has been formed does not readily release from    the Teflon®, place in a freezer, wait 5 minutes, and peel film from    Teflon®.    The film samples were allowed to age for 24 hrs before being    subjected to mechanical testing.

TABLE 4 Initial Final Prestrain Film Load @ Load @ Force Tem- SpecimenBasis 50% 50% Relax. Comp. perature¹ Width Weight Strain² Strain² (10hrs) ID (° C.) (mm) (g/m²) (N) (N) (%) 2-1 23 19.1 109 0.73 0.35 53 2-223 12.7 149 0.69 0.26 61 2-3 23 ⅜ 161 0.67 0.35 46 2-4 23 ½ 159 0.680.37 46 2-5 23 ½ 149 0.68 0.38 44 2-6 23 ½ 197 0.83 0.45 46 2-7 23 19.1106 1.18 0.66 43 ¹Temperature at which prestrain and relaxation stepswere conducted. ²Normalized to 150 g/m² and 6.4 mm width

TABLE 5 1st Cycle 2nd Cycle (200%, RT) (50%, R.T.) Com- Stress @ Setafter Force Stress @ po- Basis 200% 1st Stress @ Relaxation 30% sitionWeight Prestrain Cycle 50% @ 50% Unload ID (g/m²) (MPa) (%) (MPa) (%)(MPa) 2-1 167 2.12 14.4 1.29 9.3 0.41 2-2 150 1.80 16.5 1.15 12.0 0.312-3 173 2.54 13.8 1.37 8.3 0.45 2-4 186 2.47 16.7 1.45 12.7 0.36 2-5 1721.95 14.9 1.33 8.4 0.39 2-6 187 2.38 19.8 1.65 13.0 0.37 2-7 126 3.1324.2 2.36 24.7 0.35

The hysteresis and force data suggest a possible synergy that resultsfrom combining elastomers. For example, styrenic elastomers are known toexhibit low force relaxation over short periods of time but, over longerperiods of time relaxation becomes significant. Conversely, elastomericpolyolefins demonstrate more rapid force relaxation over short timeperiods but relaxation stabilizes over longer periods of time. As can beseen in this example, blends of these elastomers have been found toprovide a more progressive decline in force relaxation with time. In anabsorbent article context, this progressive decline provides ameaningful benefit by minimizing redmarking in the short term (lowerinitial contractive forces are required because force does not declinesubstantially with time) while providing less reduction in contractiveforce over long time periods.

Example 3

This example illustrates the possibility of modifying the tensileproperties of a commercial elastomeric polypropylene via the addition ofa commercial soft, deformable polyolefin-based material.

The following materials were compounded in a batch mixer available fromHaake Polylab of Newington, N.H. Fifty gram batches were processed forabout 6 min at 170° C. Commercially available antioxidants were alsoadded to the mix at a low level (<1%) to help protect the blend fromthermal/oxidative degradation. The following compositions (all values inwt. percent) were prepared according Table 6

TABLE 6 Composition Elastomeric Polyolefin ID Polypropylene¹ Material²LLDPE³ VLDPE⁴ 3-1 100 0 0 0 3-2 60 40 0 0 3-3 60 30 10 0 3-4 60 30 0 103-5 40 60 0 0 3-6 40 45 15 0 3-7 40 45 0 15 ¹Elastomeric polypropyleneas is available from Exxon Mobil Chemical of Huston, TX as VISTAMAXX1100. ²PARAFILM M is a polyolefin laboratory film commercialized byAmerican National Can of Chicago, IL. The film was cut into pieces priorto being added to the batch mixer. ³Linear low Density polyethylene (MI= 50 g/10 min, Density = 0.926 g/cm³,) as is available from Exxon MobilChemical of Huston, TX as LL6201. ⁴Very low density polyethylene (MI =4.5 g/10 min; Density = 0.873 g/cm³) as is available from Exxon MobilChemical of Huston, TX as EXACT 4049.

Compression-molded films were prepared with a Carver press using themethod described in Example 2. Force relaxation (Table 7) and hysteresistesting (Tables 8 and 9) was carried out according to the methodsdescribed above and the data are shown in the following tables (Aminimum of two specimens was analyzed for each reported value):

TABLE 7 Initial Final Com- Film Load @ Load @ Force posi- PrestrainSpecimen Basis 50% 50% Relax. tion Temperature^(1,2) Width WeightStrain^(3,4) Strain^(3,4) (10 hrs) ID (° C.) (mm) (g/m²) (N) (N) (%) 3-123 19 151 0.99 0.40 59 3-2 23 19 131 0.82 0.23 71 3-2 40 19 120 0.540.19 65 3-2  40³ 13 135 0.48 0.16 66 3-3 23 19 104 0.87 0.25 70 3-4 2313 124 0.89 0.26 71 3-5 23 19 109 0.58 0.14 77 3-5 40 13 97 0.46 0.14 703-6 23 19 106 1.05 0.33 69 3-7 23 13 104 1.09 0.35 68 ¹Temperature atwhich prestrain step was conducted. ²Prestrained to 300% instead of 200%³Normalized to 150 g/m² and 6.4 mm width ⁴Strained to 50% beforereaching temperature equilibrium in environmental chamber

TABLE 8 2nd Cycle (50%, R.T.) 1st Cycle % (200%, RT) Force- Stress Re- @Set laxa- Stress Com- 200% after Stress tion @ % Set posi- Basis Pre-1st @ @ 30% after tion Weight strain Cycle 50% 50% Unload 2nd ID (g/m²⁾(MPa) (%) (MPa) (%) (MPa) Cycle % 3-1 148 1.75 13.6 0.95 17.4 0.45 6.73-2 156 1.45 30.1 0.84 26.7 0.21 7.8 3-3 106 2.12 24.4 1.00 26.4 0.257.9 3-4 135 2.04 22.4 1.02 24.5 0.31 7.6 3-5 117 1.25 43.4 0.81 31.70.13 9.6 3-6 104 2.29 48.1 0.60 34.7 0.08 10.0 3-7 110 2.50 46.6 1.3424.5 0.26 7.9

TABLE 9¹ 2nd Cycle 1st Cycle (300%, RT) (200%, R.T.) Stress @ ForceComposi- Basis 300% Set after Stress @ Relaxation @ tion WeightPrestrain 1st Cycle 200% 200% ID g/m² MPa % MPa % 3-1 132 1.92 19.6 1.5018.3 3-2 161 1.69 46.5 1.82 32.7 3-3 108 2.55 36.8 2.26 31.7 3-4 1342.53 37.6 2.36 28.8 3-5 130 1.40 74.4 1.80 38.9 3-6 112 2.37 83.5 2.8041.4 3-7 112 2.76 78.4 3.37 35.1 ¹Modified hysteresis test (initial 300%cycle, followed by 2^(nd) 200% cycle (hold for 30 sec at 200%))

As can be seen, blending PARAFILM M into VISTAMAXX results in large %set values in the film as a result of pre-straining; The higher thestrain, the higher the set (>80% set for a blend containing 60% PARAFILMstrained up to 300% at room temperature). It is believed that thePARAFILM M lowers the stress required to deform the material up to agiven strain, whether during the initial cycle or at low strains insubsequent cycles. Said another way, it provides the plasto-elasticfunctionality with as soft touch and feel that nicely complement theconforming fit benefit from the VISTAMAXX. As can be seen, Adding alinear low density polyethylene component (with more or lesscrystallinity) to the blends tends to increase both loading and loadingstresses, without much influence on the amount of set and/or forcerelaxation. The % force relaxation at body temperature after 10 hrsincreases with the addition of PARAFILM, an indication of a partial lossin the elastic/recoverable characteristics of the material.

Table 10 illustrates the amount of permanent deformation (expressed interms of specimen length relative to initial sample length) for theabove material compositions when subjected to 2 successive deformationcycles up to 300% or 500% (of the original sample length in bothdeformations) at room temperature (˜23° C.). Compression-molded filmsamples were used having 5 mm width and 2 cm length. The samples werehand-strained to a first stretch dimension (i.e. 300% for 3-1, 500% forthe plasto-elastic compositions 3-2 to 3-7), held for 3 sec and allowedto relax for 5 min before the operation was repeated.

TABLE 10 First First Second Second Composi- Initial Stretch RelaxedStretch Relaxed tion Dimension Dimension Dimension Dimension DimensionID (cm; %) (cm; %) (cm; %) (cm; %) (cm; %) 3-1 2; 100%  6; 300% 2.3;115%  6; 300%  2.3; 11.5% 3-2 2; 100% 10; 500% 3.1; 155% 10; 500% 3.15;158% 3-3 2; 100% 10; 500% 3.1; 155% 10; 500%  3.2; 160% 3-4 2; 100% 10;500% 3.0; 150% 10; 500% 3.15; 158% 3-5 2; 100% 10; 500% 3.7; 185% 10;500% 3.85; 193% 3-6 2; 100% 10; 500% 4.5; 225% 10; 500% 4.65; 233% 3-72; 100% 10; 500% 4.6; 230% 10; 500% 4.75; 238%

As can be seen, the plasto-elastic blends (3-2 to 3-7) exhibit anincrease in permanent size in the range of 50% to 125% as the result ofthe incorporation of various amounts of PARAFILM. The addition of LLDPEor VLDPE to PARAFILM further enhances the % set in blends when PARAFILMis the majority component of the blend. It should also be noted that setdoes not substantially increase on an additional strain cycle. Forexample, the difference in % set between the first and second cycle istypically less than 10% and often less than 5%. This is an indication ofthe excellent dimensional stability of the plasto-elastic compositionbeyond the prestraining cycle. Said another way, there is substantiallyelastic behavior after the first prestraining cycle.

Example 4

This example illustrates the effect on a variety of elastomericmaterials due to the addition of a commercial soft, deformablepolyolefin-based material (PARAFILM M).

The following materials were compounded in a batch mixer available fromHaake Polylab of Newington, N.H. Fifty gram batches were processed forabout 6 min at 170° C. Commercially available antioxidants were alsoadded to the mix at a low level (<1%) to help protect the blend fromthermal/oxidative degradation. Table 11 describes the compositions thatwere prepared (all values in wt. percent).

TABLE 11 Very Styrenic Low Linear Com- Block Density Low Metal- posi-Co- Poly- Density locene tion Polyolefin polymer ethyl- Poly- Poly- IDMaterial¹ Blend² ene³ ethylene⁴ VLDPP⁵ propylene⁶ 4-1 40 60 4-2 60 404-3 40 51 9 4-4 60 34 6 4-5 40 51 9 4-6 60 34 6 4-7 50 30 17 3 4-8 50 3017 3 4-9 50 25 21.25 3.75 ¹PARAFILM M is a polyolefin laboratory filmcommercialized by American National Can of Chicago, IL. The film was cutinto pieces prior to being added to the batch mixer. ²A high-performanceblend typically used in diaper stretch components. It consists of aStyrenic Block Copolymer available from Kuraray Co. Ltd. of Tokyo, Japanas Septon 4033, a polystyrene grade from Nova Chemicals of Pittsburgh,PA as PS3190 and an oil available from Penreco of The Woodlands, TX asDrakeol 600 that are blended together at a 55/10/35 ratio. ³EXACT 4049(MI = 4.5 g/10 min; Density = 0.873 g/cm³) available from Exxon MobilChemical Co of Huston, TX. ⁴LL6201 (MI = 50 g/10 min, Density = 0.926g/cm³,) available from Exxon Mobil Chemical Co of Huston, TX. ⁵VLDPPMARS 3900 (MFR~ 3 g/10 min; density = 0.862 g/cm³) is a very low densitypolypropylene material that is described in U.S. Pat. No. 6,555,643. ⁶Ametallocene polypropylene (MFR = 8 g/10 min; Density = 0.950 g/cm³) asis available from Atofina Petrochemicals of Huston, TX as EOD-00-07.Note that in the case of the very low crystallinity polyolefinmaterials, a small fraction (up to about 15% in the composition createdabove) of a higher crystallinity material may be added

Compression-molded films were prepared with a Carver press using themethod described in Example 2. Force relaxation (Table 12) andhysteresis testing (Table 13) was carried out according to the methodsdescribed above and the data are shown in the following tables (Aminimum of two specimens was analyzed for each reported value):

TABLE 12 Pre- Initial Final Force Com- strain Film load @ load Relax.posi- Temper- Specimen Basis 50% @ 50% after tion ature Width weightstrain^(1,2) strain^(1,2) 10 hrs ID (° C.) (mm) (g/m²) (N) (N) (%) 4-123 13 118 0.57 0.23 60 4-2 23 13 152 0.63 0.22 66 4-3 23 ¼ 118 2.68 1.0860 4-4 23 13 144 2.19 0.80 63 4-5 23 13 133 0.99 0.31 68 4-6 23 25 1080.84 0.25 70 4-7 23 13 140 1.23 0.51 59 4-8 23 13 130 0.74 0.30 60 4-923 13 124 0.78 0.23 71 ¹Normalized to 150 g/m² and 6.4 mm width²Strained to 50% before reaching temperature equilibrium inenvironmental chamber

TABLE 13 1st Cycle 2nd Cycle (200%, RT) (50%, R.T.) % Set % Force Stress% Com- Stress @ after Stress Relax- @ Set posi- Basis 200% 1st @ ation30% after tion Weight Prestrain Cycle 50% @ 50% Unload 2nd ID g/m² MPa %MPa % MPa Cycle % 4-1 137 1.71 15 0.82 17.2 0.35 7.2 4-2 114 1.21 300.53 26.5 0.13 8.5 4-3 125 4.03 89 3.69 25.4 0.60 10.0 4-4 139 3.61 983.44 28.3 0.40 12.4 4-5 143 2.60 41 1.24 36.8 0.15 8.0 4-6 123 2.04 671.26 43.2 0.04 12.5 4-7 133 2.21 64 1.50 23.9 0.35 8.3 4-8 138 1.78 310.82 29.7 0.17 7.4 4-9 137 1.59 38.5 0.82 31.8 0.13 9.9

As can be seen, adding PARAFILM M results in large % set values in thefilm during prestraining for a variety of elastomeric materials. Atcomparable PARAFILM/elastomer blend compositions, the styrene blockcopolymer-based blend exhibits the least amount of set as well as thelowest amount of force relaxation, whether the latter is measured atroom temperature after 30 sec or after 10 hrs at body temperature.Normalized load values also remain relatively low. The elastomericpolypropylene-based grades (Blends 2 and 5 of Example 3) exhibit higherset values, somewhat higher force relaxation as well as slightly higherload values. The elastomeric polyethylene blends exhibit the highest %set values (large shaping component), high load values and relativelylow force. Also, tri-component blends that combine PARAFILM with twodifferent types of elastomers (as illustrated by compositions 4-7 to4-9) may be created to further tailor the balance of properties of theblend to those required for any specific application.

Example 5

This example illustrates the effect on tensile properties of acommercial elastomeric polypropylene grade (VISTAMAXX) by the additionof wax/polyolefin mixtures.

The following blends were compounded in a batch mixer available fromHaake. Polylab of Newington, N.H. Fifty gram batches were processed forabout 6 min at 170° C. Commercially available antioxidants were alsoadded to the mix at a low level (<1%) to help protect the blend fromthermal/oxidative degradation. Compositions according Table 14 wereprepared (values expressed in weight %).

TABLE 14 Blend Component Elastomeric PP Low Very Low PolypropyleneLinear Low Micro- Low Molecular Molecular Molecular Composition RandomReactor Blend Density crystalline Weight Weight Polypropylene Weight IDCopolymer¹ Polypropylene² Polyethylene³ Wax⁴ Polyethylene/Wax⁵Polyethylene⁶ Wax⁷ Polyisobutylene⁸ 5-1 60 8 24 8 5-2 60 8 32 5-3 60 832 5-4 50 10 8 32 5-5 40 12 48 5-6 60 20 20 5-7 60 10 10 20 ¹Availablefrom Exxon Mobil Chemical of Huston, TX as VISTAMAXX 1100. ²Softpolypropylene-based thermoplastic elastomer reactor blend produced usingCatalloy technology and available as ADFLEX 7353 from Basell Polyolefinsof Elkton, MD. ³Linear low density polyethylene (Melt Index = 50 g/10min, Density = 0.926 g/cm³) as is available as LL6201 from Exxon MobilChemical Co of Huston, TX. ⁴Microcrystalline wax available from theCrompton Corporation of Middlebury, CT as MULTIWAX W-835. ⁵Refined Wax128 is a low melting refined petroleum wax available from the ChevronTexaco Global Lubricants of San Ramon, CA. ⁶A low molecular weightpolyethylene as is available for Honeywell Specialty wax and additivesof Morristown, NJ as A-C 735. ⁷A low molecular weight polypropylene asis available from Clariant, Pigments & Additives Division of Coventry,RI as LICOWAX PP230. ⁸A very low molecular weight polyisobutylene as isavailable from BASF of Ludwigshafen, Germany as OPPANOL B.

Compression-molded films were prepared with a Carver press using themethod described in Example 2. Force relaxation and hysteresis testingwas carried out according to the methods described above and the dataare shown in Tables 15 and 16 below (minimum of two specimens):

TABLE 15 Initial Final Film load load Force Compo- Prestrain SpecimenBasis @ 50% @ 50% Relax- sition Temperature Width Weight Strain¹ Strain¹ation ID (° C.) (mm) (g/m²) (N) (N) (%) 5-1 23 25 115 0.39 0.11 72 5-223 25 107 0.46 0.16 66 5-3 23 25 118 0.43 0.13 70 5-4 23 25 122 0.650.28 57 5-5 23 25 86 0.64 0.24 62 5-6 23 13 137 0.79 0.31 60 5-7 23 13126 0.95 0.45 53 ¹Normalized to 150 g/m² and 6.4 mm width

TABLE 16 1st Cycle (200%, RT) 2nd Cycle % Set (50%, R.T.) Stress @ afterStress % Force Stress @ Basis 200% 1st @ Relaxation 30% CompositionWeight Prestrain Cycle 50% @ 50% Unload ID g/m² MPa % MPa % MPa 5-1 1241.56 29.3 0.78 30.0 0.15 5-2 115 1.62 39.3 0.94 30.6 0.15 5-3 132 1.1128.4 0.64 29.0 0.14 5-4 131 2.07 39.3 1.10 32.3 0.16 5-5 90 1.92 94.91.63 45.8 0 5-6 131 1.86 20.4 1.02 21.9 0.39 5-7 127 2.59 24.5 1.16 27.50.35

As can be seen, various combinations of high molecular weightpolyethylene, molecular weight polyethylene, polyethylene wax andpolypropylene wax can be blended with a polypropylene-based elastomer toprovide a blend with a combination of plastic and elastic properties.Adding a fraction of reactor blend elastomeric polypropylene not onlylowers the amount of force relaxation but also increases stress values.

Example 6

This example describes film formation from blends of an isotacticpolypropylene with stereoerrors along the polymer chain as disclosed inU.S. Pat. No. 6,555,643 the isotactic polypropylene resin was blendedwith various modifiers as described in Table 17. Samples 6-1 to 6-5 werecompounded (including commonly used stabilizer materials such asantioxidants and the like at <1% of the blend) using a laboratory-scalemixer available from C. W. Brabender Instruments of Hackensack, N.J. Thefilms were compression molded into films having a thickness of ˜200μ byheating to ˜200° C. and compressing between PTFE sheets in a CarverPress using a method similar to steps 1 through 14 in the HysteresisTest method described below.

TABLE 17 Composition Polymer According to U.S. Pat. No. 6,555,643Modifier ID (%) (%) 6-1 100 — 6-2 85 15^(a) 6-3 70 30¹ 6-4 55 45¹ 6-5 7030² ¹Experimental metallocene polypropylene having a melt flow rate of 8grams/10 minutes from Ato-Fina Chemicals of Houston TX as code EOD 00-07²Polypropylene-based nanoclay concentrate available from PolyOne ofArlington Heights, IL PolyOne 1001 master batch concentrate (50% clay).The properties according to the Hysteresis Test for these blends areshown in Table 18.

TABLE 18 1st Cycle (200%, RT) 2nd Cycle Stress % (50%, R.T.) @ SetStress 200% after Stress % Force @ % Set Compo- Basis Pre- 1st @Relaxation 30% after sition Weight strain Cycle 50% @ 50% Unload 2nd IDg/m² MPa % MPa % MPa Cycle %  6-1¹ 154 2.74 3.9 1.24 18.8 0.64 6.7 6-2185 3.49 17.8 1.81 28.3 0.60 5.0 6-3 192 6.93 34.8 3.04 42.2 0.28 11.36-4 167 8.91 76.0 7.51 55.2 0.19 12.0 6-5 167 7.15 30.7 2.80 43.7 0.308.2 ¹Data same as Blend 1-2

Example 7

This example demonstrates spinning of fibers from polyolefin elastomerblends and plasto-elastic blends according to the present invention.Fibers were spun from: 1) a random polypropylene copolymer resin(available from Exxon Mobil Chemical of Huston, Tex. as VISTAMAXX 1120)and 2) a plasto-elastic material according to the present invention(same composition as 5-7 of Example 5) using a two extruder system,where each extruder is a horizontal single-screw extruder. The extrudaterate from each extruder to the spinpack is controlled by a metering meltpump that feeds a 4-hole spin pack (Hills Incorporated, W. Melbourne,Fla.). Table 19 lists the extrusion conditions that were found to leadto successful fiber formation:

TABLE 19 Extruder Condition 7-1 7-2 Extruder ° C. 135-180 135-180Temperature Range Melt Temp. ° C. 185 185 Melt Pressure MPa 10.3 10.3Spinpack Melt ° C. 200 195 Temp Spinpack Pressure MPa <21 <21 MassThroughput g/h/min 0.3 0.3Fibers were successfully spun using both of these materials atattenuating air pressures of up to 483 kPa (70 psi).

Example 8

This example is intended to demonstrate formation of a nonwoven webcomprising the plasto-elastic material of the present invention.

A small web was produced using the 4-hole fiber spinning line describedabove. Bicomponent fibers (core=25% a random polypropylene copolymer(VISTAMAXX 2100 from Exxon Mobil Chemical of Huston, Tex.) and shell=75%of the plasto-elastic formulation 5-7) were spun using an attenuatingair pressure of 40 psi. Spun fibers were first gathered on a small-scalemoving table and bonded ultrasonically using a bonding device assembledby Machinetek of Fairfield, Ohio that incorporates a Branson 900 BCAUltrasonic Probe (Branson Ultrasonic Corporation of Danbury, Conn.). Thewebs were bonded at a pressure of 276 KPa. The amplitude of the signal(dial position 50) and the speed of the web (dial position 8) definedultrasonic energy and residence time respectively. Increased amplitude,higher pressure and smaller web speed all contribute to higher bondingThe resulting nonwoven web had a basis weight of about 49.2 g/m².

The results of a two cycle hysteresis evaluation of the web (extensionto 150% at room temperature (˜23° C.)) are shown in FIG. 1 where 10 isthe extension portion of the first cycle, 14 is the return portion ofboth cycles (it should be noted that the web follows the same returnpath for both cycles) and 12 is the extension portion of the secondcycle. In this figure load L in Newtons is plotted against percentelongation S. The percent set (˜30%) due to the first extension cyclecan be seen in the starting point of the second cycle. Additional cycles(not shown) indicate the web follows substantially the same curve as 12on extension and 14 on return with only minimal (<15%) additional set.

Example 9

This example is intended to demonstrate formation of a film comprisingthe plasto-elastic material of the present invention.

The plasto-elastic formulation according to the present invention(Composition 5-7 from Example 5) was extruded into a film on a lab-scaleHaake Polylab extrusion apparatus (available from Thermo Electron(Karlsruhe), Karlsruhe, Germany) with a flat die and take-off unit setup for a line speed of 21 m/min. The film was collected on a roll ofrelease paper. The film had a caliper of about 76μ and width of about11.4 cm.

The results of a two cycle hysteresis evaluation of the film (extensionto 200% at room temperature (˜23° C.)) are shown in FIG. 2 where 20 isthe extension portion of the first cycle, 24 is the return portion ofboth cycles (it should be noted that the web follows the same returnpath for both cycles) and 22 is the extension portion of the secondcycle. In this figure load L in Newtons is plotted against percentelongation S. The percent set (˜35%) due to the first extension cyclecan be seen in the starting point of the second cycle. Additional cycles(not shown) indicate the film follows substantially the same curve as 12on extension and 14 on return with only minimal (<15%) additional set.

Test Methods Apparatus

-   Tensile Tester: A commercial constant rate of extension tensile    tester from Instron Engineering Corp., Canton, Mass. or SINTECH-MTS    Systems Corporation, Eden Prairie, Minn. (or a comparable tensile    tester) may is suitable. The instrument is interfaced with a    computer for controlling the test speed and other test parameters,    and for collecting, calculating and reporting the data.-   Load Cell Choose the jaws and load cell suitable for the test; the    jaws should be wide enough to fit the sample, typically 2.54 cm jaws    are used; the load cell is chosen so that the expected tensile    response from the sample tested will be between 25% and 75% of the    capacity of the load cells or the load range used, typically a 1 kN    load cell is used;-   Sample Cutter The specific sample cutter is defined by the desired    sample width. Suitable cutters are available from Thwing-Albert    Instrument Co. of Philadelphia, Pa. For a 2.54 cm wide sample a    Model JDC 1-10 is suitable.

Sample Preparation

The plasto-elastic material is first separated from any substrate orother material to which it is attached by any suitable means. One suchmeans is to freeze the sample so as to reduce the bond strength betweenthe plasto-elastic material and other materials. A suitable freezingmedium is compressed 1,1,1,2 tetrafluoroethane sold under the trade nameQUICK-FREEZE by Miller-Stephenson Chemical Company of Danbury, Conn.

Separate enough sample to prepare at least three specimens 2.5 cm×5 cm(˜15 grams). The Specimens are prepared using the following method:

-   -   1) Weigh approximately 12 grams of the elastomeric composition        of interest.    -   2) Compression mold the composition by placing the pre-weighed        material between two pieces of 0.010 inch (0.03 mm) caliper PTFE        (Teflon®) film.    -   3) Place the film “sandwich” between preheated aluminum plates        that are inserted into a Carver Press model 3853-0 with heated        plates set to approximately 200° C.    -   Heat the material for 3 minutes and then pressing it between the        plates with an applied pressure of 17 MPa.    -   5) Allow the formulation to flow under pressure for 30 seconds.    -   6) Quench the resulting film to ambient temperature.    -   7) Cut the sample into three equal portions.    -   8) Place each portion between films of PTFE and preheated        aluminum plates and allowed to heat up to 160° C. for 1 minute        in the Carver press before 14 MPa of pressure is applied.    -   9) Allow the sample to flow under pressure for 30 seconds.    -   10) Release the pressure is removed and rotate the sample 90°.        Insert the sample back into the press and immediately apply a        pressure of 21 MPa.    -   11) The sample is again allowed to flow for 30 seconds. The        pressure is released and the sample is flipped, inserted back        into the press and immediately 28 MPa of pressure is applied.    -   12) The sampled is again allowed to flow for 30 seconds.    -   13) The pressure is removed and the sample is rotated 90° and        inserted back into the press and immediately 34 MPa psi of        pressure is applied.    -   14) The sample is again allowed to flow for 30 seconds.    -   15) After the final pressing, the sample is allowed to cool to        ambient temperature. The resulting film thickness is between 4        mils up to 15 mils thick    -   16) Cut the resulting sample into a 2.5 cm×5 cm rectangle.        All testing is done at ambient laboratory conditions (˜25° C.,        50% RH).

First Strain (Shaping Strain) Hysteresis Cycle:

-   1) Samples are placed in the tensile tester jaws with a 2.5 cm gauge    length. Otherwise, mount the sample between the jaws of the tensile    tester using the maximum gap allowed by the sample length.-   2) Strain the sample to a maximum strain of 200% (i.e., the sample    is 3× its initial length) at a strain rate of 25.4 cm/min.    Particular samples may be strained to other maximum strains in    specific instances. If a maximum strain other than 200% is used,    that strain should be recorded and used in the % Set calculation.-   3) At 200% strain (7.5 cm jaw separation) the direction of jaw    displacement is reversed and the jaw returns to its original    position at a rate of 25.4 cm./min.-   4) Allow the sample to relax at zero strain for one minute.-   5) After one minute, the samples are reloaded at a strain rate of    25.4 cm./min up to a load of 0.10 N to pull out slack in the sample.    Measure and record the separation between the jaws.-   6) Calculate % set according to the following equation (The % set    determines the extent of permanent plastic deformation built into    the material as a result of the pre-straining process.):

${\% \mspace{14mu} {Set}} = {\left\lbrack \frac{{{Jaw}\mspace{14mu} {Gap}\mspace{14mu} {after}\mspace{14mu} {Step}\mspace{14mu} 5} - {{Gage}\mspace{14mu} {Length}}}{{Gage}\mspace{14mu} {Length}} \right\rbrack \times 100}$

-   7) A minimum of 3 samples is tested and the data averaged.-   8) Report the following:    -   i) Maximum load at 200% strain (or other value of maximum        strain) in N/cm.    -   ii) % set (As will be recognized, the difference (100-% set) in        turn provides the % extent of recoverable elastic deformation        intrinsic to the material.)

Second Strain Hysteresis Cycle:

-   1) Clamp a sample prestrained according to the First Hysteresis    Loading Cycle between a pair of jaws with set to a gage length of    2.5 cm pulling gently to remove any slack.-   2) After 2 minutes, extend the sample to 50% strain (1.5×initial    length) at a rate of 25 cm/min.-   3) Hold the sample at 50% strain for a period of 30 seconds and the    force is monitored (e.g., collected by the associated computer) as a    function of time over that period.-   4) Return to the original length at 10 in./min and hold for 60    seconds.-   5) After one minute, the samples are reloaded at a strain rate of    25.4 cm./min up to a load of 0.10 N to pull out slack in the sample.    Measure and record the separation between the jaws.-   6) Measure the % set upon reloading following the same protocol    described in the method outlined above.

${\% \mspace{14mu} {Set}} = {\left\lbrack \frac{{{Jaw}\mspace{14mu} {Gap}\mspace{14mu} {after}\mspace{14mu} {Step}\mspace{14mu} 5} - {{Gage}\mspace{14mu} {Length}}}{{Gage}\mspace{14mu} {Length}} \right\rbrack \times 100}$

-   7) A minimum of 3 samples is tested and the data averaged.-   8) Report the following for each of three samples:    -   a. The load at 50% strain (N/cm)    -   b. % set    -   c. % force relaxation at 50% during the 30 second hold time in        the second hysteresis cycle; It is determined using the        following formula:

${\% \mspace{14mu} {Force}\mspace{14mu} {relaxation}} = \frac{\begin{bmatrix}{\left( {{Load}\mspace{14mu} {at}\mspace{20mu} 50\% \mspace{20mu} {before}\mspace{14mu} {hold}\mspace{14mu} {time}} \right) -} \\\left( {{Load}\mspace{14mu} {at}\mspace{14mu} 50\% \mspace{20mu} {after}\mspace{14mu} {hold}\mspace{14mu} {time}} \right)\end{bmatrix}}{\left( {{Load}\mspace{14mu} {at}\mspace{14mu} 50\% \mspace{20mu} {before}\mspace{14mu} {hold}\mspace{14mu} {time}} \right)}$

Force Relaxation at Body Temperature (38° C.):

-   1) Clamp a sample prestrained according to the First Hysteresis    Loading Cycle between a pair of jaws with set to a gage length of    2.5 cm pulling gently to remove any slack. For this test the jaws    and sample are in an environmental chamber maintained at 38° C. and    the sample is allowed to equilibrate in the chamber (˜1 minute)    before it is extended.-   2) Extend the sample to 50% strain (1.5×initial length) at a rate of    25 cm/min.-   3) Hold the sample at 50% strain for a period of 10 hours-   4) Monitor and record the initial force after the extension step and    the force at 1, 4 and 10 hrs at 38° C.-   5) Calculate and report % force relaxation for three samples at each    time period, using the following equation:

${\% \mspace{14mu} {Force}\mspace{14mu} {relaxation}\mspace{11mu} \left( {{{{at}\mspace{14mu} 38\mspace{14mu} {C.}}\&}\mspace{14mu} {at}\mspace{14mu} {time}\mspace{14mu} t} \right)} = \frac{\begin{bmatrix}{\left( {{Inital}\mspace{14mu} {load}\mspace{14mu} {at}\mspace{14mu} 50\%}\; \right) -} \\\left( {{Load}\mspace{14mu} {at}\mspace{14mu} {time}\mspace{14mu} t} \right)\end{bmatrix}}{\left( {{Initial}\mspace{14mu} {load}\mspace{14mu} {at}\mspace{14mu} 50\%}\; \right)}$

Dimensional Stability in Storage Conditions

This method is based on ASTM standard method D 1204-02:

-   1) Prestrain a sample according to the First Hysteresis Loading    Cycle-   2) Carefully measure the length and width dimensions of the sample    and a permanent marker is used to trace equidistant points at 10 or    5 mm intervals (depending upon the initial size of the specimens) in    both dimensions.-   3) Place the sample on a sand bed (replaces paper and talc of the    ASTM method) and into a controlled thermal chamber at a temperature    of 60° C.-   4) Remove the sample after two minutes.-   5) Measure both dimensions after the exposure to 60° C.-   6) Calculate the change in both dimensions as a percentage of the    original dimension. A value above 100% is indicative of an expansion    of the material in that particular direction as a result of exposure    to heat (annealing). A value lower than 100% is indicative of a    contraction of the specimen.-   7) Report the results for three samples.

All documents cited in the Detailed Description of the Invention are, inrelevant part, incorporated herein by reference; the citation of anydocument is not to be construed as an admission that it is prior artwith respect to the present invention.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1. A stretch laminate comprising: a first fibrous nonwoven layer; and an extruded web joined to said first fibrous nonwoven layer, wherein said extruded web is a film comprising a plasto-elastic material wherein said plasto-elastic material comprises a combination of an elastomeric polypropylene and a second polyolefin, said combination being selected from polymeric blends or polymeric mixtures, such that a) said extruded web is provided with a set of at least 30% when subjected to an initial strain cycle, and b) said extruded web has substantially elastic properties when a sample taken from said extruded web is subjected to at least a second strain cycle.
 2. The stretch laminate according to claim 1 wherein said elastomeric polypropylene is a polypropylene polymer comprising crystalline isotactic blocks and amorphous atactic blocks.
 3. The stretch laminate according to claim 1 wherein said second polyolefin is a polyolefin wax.
 4. The stretch laminate according to claim 1 wherein at least a portion of said stretch laminate is subjected to a shaping strain cycle.
 5. The stretch laminate according to claim 1 wherein said first fibrous nonwoven layer comprises spunbond fibers.
 6. The stretch laminate according to claim 1 wherein the fibers of said first fibrous nonwoven layer comprises a polyolefin material.
 7. The stretch laminate according to claim 1 wherein said extruded web is provided with a set of less than 15% after relaxation from a second strain of 50%.
 8. The stretch laminate according to claim 7 wherein said extruded web is provided with a set of less than 10% after relaxation from a second strain of 50%.
 9. The stretch laminate according to claim 1 wherein after relaxation from said initial strain cycle, said extruded web exhibits less than about 70% force relaxation, while held at 50% strain for 4 hours at 38° C.
 10. The stretch laminate according to claim 1 wherein said film is a coextruded film having at least one additional layer.
 11. A method for making a stretch laminate comprising: extruding a web to form a film comprising a plasto-elastic material wherein said film of plasto-elastic material is such that a) said film is provided with a set of at least 30% when subjected to an initial strain cycle, b) said film has substantially elastic properties when a sample taken from said extruded web is subjected to at least a second strain cycle; joining said film to a first fibrous nonwoven layer.
 12. The method according to claim 11 wherein said plasto-elastic material comprises a combination of an elastomeric polypropylene and a second polyolefin, said combination being selected from polymeric blends or polymeric mixtures.
 13. The method according to claim 12 wherein said elastomeric polypropylene is a polypropylene polymer comprising crystalline isotactic blocks and amorphous atactic blocks.
 14. The method according to claim 12 wherein said second polyolefin is a polyolefin wax.
 15. The method according to claim 11 wherein at least a portion of said stretch laminate is subjected to a shaping strain cycle.
 16. The method according to claim 11 wherein said first fibrous nonwoven layer comprises spunbond fibers.
 17. The method according to claim 11 wherein the fibers of said first fibrous nonwoven layer comprises a polyolefin material.
 18. The method according to claim 11 wherein said extruded web is provided with a set of less than 15% after relaxation from a second strain of 50%.
 19. The method according to claim 11 wherein after relaxation from said initial strain cycle, said extruded web exhibits less than about 70% force relaxation, while held at 50% strain for 4 hours at 38° C.
 20. A stretch laminate comprising: a first fibrous nonwoven layer; and an extruded web joined to said first fibrous nonwoven layer, wherein said extruded web is a film comprising a combination of an elastomeric polypropylene and a second polyolefin, said combination being selected from polymeric blends or polymeric mixtures, such that a) said extruded web is provided with a set of at least 30% when subjected to an initial strain cycle, and b) said extruded web has substantially elastic properties when a sample taken from said extruded web is subjected to at least a second strain cycle. 